backend/extension: Introduce new extension backend #701
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Pretty neat. Cool :) |
gunjan5
suggested changes
May 16, 2017
Documentation/extension.md
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| * `Type` (string): `extension` | ||
| * `PreStartupCommand` (string): Command to run before allocating a network to this host | ||
| * The stdout of the process is captured and passed to the stdin of the SubnetAdd/Remove commands. | ||
| * `PostStartupCommand` (string): Command to run before allocating a network to this host |
Documentation/extension.md
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| * `SubnetAddCommand` (string): Command to run when a subnet is added | ||
| * stdin - The output from `PreStartupCommand` is passed in. | ||
| * The following environment variables are set | ||
| * SUBNET - The subnet on the remote host that was added. |
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do you mean subnet of instead of subnet on?
Documentation/extension.md
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| * `SubnetRemoveCommand`(string): Command to run when a subnet is removed | ||
| * stdin - The output from `PreStartupCommand` is passed in. | ||
| * The following environment variables are set | ||
| * SUBNET - The subnet on the remote host that was removed. |
backend/extension/extension.go
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| @@ -0,0 +1,150 @@ | |||
| // Copyright 2015 flannel authors | |||
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shouldn't the license headers be 2017?
backend/extension/extension.go
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| log.Infof("Ran command: %s\n Output: %s", n.postStartupCommand, cmd_output) | ||
| } | ||
| } else { | ||
| log.Infof("No pre startup command configured - skipping") |
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this should be post startup, not pre
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The
extensionbackend provides an easy way for prototyping new backend types for flannel.It is not recommended for production use, for example it doesn't have a built in retry mechanism.
This backend has the following configuration
Type(string):extensionPreStartupCommand(string): Command to run before allocating a network to this hostPostStartupCommand(string): Command to run before allocating a network to this host* SUBNET - The subnet on the remote host that was added.
SubnetAddCommand(string): Command to run when a subnet is addedPreStartupCommandis passed in.SubnetRemoveCommand(string): Command to run when a subnet is removedPreStartupCommandis passed in.All commands are run through the
shshell and are run with the same permissions as the flannel daemon.Simple example (host-gw)
To replicate the functionality of the host-gw plugin, there's no need for a startup command.
The backend just needs to manage the route to subnets when they are added or removed.
An example
{ "Network": "10.0.0.0/16", "Backend": { "Type": "extension", "SubnetAddCommand": "ip route add $SUBNET via $PUBLIC_IP", "SubnetRemoveCommand": "ip route del $SUBNET via $PUBLIC_IP" } }Complex example (vxlan)
VXLAN is more complex. It needs to store the MAC address of the vxlan device when it's created and to make it available to the flannel daemon running on other hosts.
The address of the vxlan device also needs to be set after the subnet has been allocated.
An example
{ "Network": "10.50.0.0/16", "Backend": { "Type": "extension", "PreStartupCommand": "export VNI=1; export IF_NAME=flannel-vxlan; ip link del $IF_NAME 2>/dev/null; ip link add $IF_NAME type vxlan id $VNI dstport 8472 && cat /sys/class/net/$IF_NAME/address", "PostStartupCommand": "export IF_NAME=flannel-vxlan; export SUBNET_IP=`echo $SUBNET | cut -d'/' -f 1`; ip addr add $SUBNET_IP/32 dev $IF_NAME && ip link set $IF_NAME up", "SubnetAddCommand": "export SUBNET_IP=`echo $SUBNET | cut -d'/' -f 1`; export IF_NAME=flannel-vxlan; read VTEP; ip route add $SUBNET nexthop via $SUBNET_IP dev $IF_NAME onlink && arp -s $SUBNET_IP $VTEP dev $IF_NAME && bridge fdb add $VTEP dev $IF_NAME self dst $PUBLIC_IP" } }